Cool-tip thermocouple including two-piece hub

ABSTRACT

An ablation electrode system includes a handle assembly; a needle electrode assembly supported in and extending from the handle assembly. The needle electrode assembly includes an outer tube having at least a conductive distal tip and defining a cavity therein; and an inner tube disposed at least partially within the cavity of the outer tube and defining a lumen therein. The ablation electrode assembly includes a hub assembly fluidly connected to the needle electrode assembly. The hub assembly defines a first chamber and a second chamber; wherein the proximal end portion of the inner tube is in fluid communication with the first chamber and the proximal end portion of the outer tube is in fluid communication with the second chamber. The ablation electrode assembly includes a first fluid conduit fluidly connected to the first chamber; and a second fluid conduit fluidly connected to the second chamber.

BACKGROUND

1. Technical Field

The present disclosure relates to electrode thermosurgery systems and,more particularly, to cool-tip ablation electrode systems used forthermosurgery procedures and the like.

2. Background of Related Art

Therapeutic lesions in living bodies have been accomplished for manydecades using radio-frequency (RF) and other forms of energy. Theprocedures have been particularly useful in the field of neurosurgery,typically where RF ablation needle electrodes (usually of elongatedcylindrical geometry) are inserted into a living body. A typical form ofsuch needle electrodes incorporates an insulated sheath from which anexposed (uninsulated) tip extends.

Generally, the ablation electrode is coupled between a grounded RF powersource outside the body and a reference ground or indifferent electrodefor contacting a large surface of the body. When an RF voltage isprovided between the reference electrode and the inserted ablationelectrode, RF current flows from the needle electrode through the body.Typically, the current density is very high near the tip of the needleelectrode, which heats and destroys the adjacent tissue.

In the past, RF ablation electrode systems have incorporated temperaturesensors, for example, in the form of a thermistor or thermocouple. Inthat regard, reference may be made to U.S. Pat. No. 4,411,266 to Cosman,the entire contents of which are incorporated herein by reference, for adetailed discussion of the same. Typically, the sensor is connected to amonitoring apparatus for indicating temperature to assist inaccomplishing a desired lesion. As generally known, for a given tipgeometry and tip temperature, lesions of a prescribed size can be madequite consistently.

A limitation of prior electrode ablation systems relates to thetemperature of the tip. Specifically, prior needle electrodes of a giventip geometry never should effectively exceed a temperature of 100° C. Atthat temperature, the surrounding tissue will boil and char. Also,uncontrolled disruption, such as hemorrhage and explosive gas formation,may cause extremely hazardous and clinically dangerous effects on thepatient. Consequently, the lesion size for a given electrode geometrygenerally has been considered to be somewhat limited by the fact thatthe tissue near the tip must not exceed 100° C.

Essentially, during RF ablation, the needle electrode temperature ishighest near the tip, because the current density is the highest at thatlocation. Accordingly, temperature falls off as a function of distancefrom the tip of the needle electrode, and except for possibleabnormalities in tissue conductivity and so on, in a somewhatpredictable and even calculable pattern. As an attendant consequence,the size of RF lesions for a given electrode geometry have been somewhatlimited.

One proposed solution to the limitation of lesion's size has been toemploy “off-axis” electrodes, for example the so called ZervasHypophysectomy Electrode or the Gildenberg Side-Outlet electrode, asmanufactured by Radionics, Inc., Burlington, Mass. However, suchsystems, in requiring multiple tissue punctures, increase the risk ofhemorrhage, severely prolong the time of surgery and increase the levelof delicacy. Also, an umbrella of off-axis lesions may not produce adesired homogenous or uniform lesion.

SUMMARY

The present disclosure relates to ablation electrode systems used forthermosurgery procedures and the like.

According to one aspect of the present disclosure, an ablation electrodesystem for use with a source of electrosurgical energy to ablate tissuein a living subject is provided. The ablation electrode system includesa handle assembly; and a needle electrode assembly supported in andextending from the handle assembly. The needle electrode assemblyincludes an outer tube having at least a conductive distal tip, aproximal end portion supported in the handle assembly, and defining acavity therein; and an inner tube disposed at least partially within thecavity of the outer tube and having a proximal end portion supportedwithin the handle assembly, the inner tube defining a lumen therein.

The ablation electrode system further includes a hub assembly supportedwithin the handle assembly and fluidly connected to the needle electrodeassembly. The hub assembly includes an outer shell defining a lumentherein; and an inner manifold operatively supported in the lumen of theouter shell. The inner manifold and the outer shell are configured anddimensioned so as to define a first chamber and a second chambertherebetween. The proximal end portion of the inner tube is in fluidcommunication with the first chamber and the proximal end portion of theouter tube is in fluid communication with the second chamber.

The ablation electrode system further includes an electrical conduitelectrically connected to the outer tube of the needle electrodeassembly; a first fluid conduit fluidly connected to the first chamber;and a second fluid conduit fluidly connected to the second chamber.

According to another aspect of the present disclosure, an ablationelectrode system is provided and includes a handle assembly; a needleelectrode assembly supported in and extending from the handle assembly.The needle electrode assembly includes an outer tube having at least aconductive distal tip, a proximal end portion supported in the handleassembly, and defining a cavity therein; and an inner tube disposed atleast partially within the cavity of the outer tube and having aproximal end portion supported within the handle assembly, the innertube defining a lumen therein.

The ablation electrode assembly includes a hub assembly supported withinthe handle assembly and fluidly connected to the needle electrodeassembly. The hub assembly defines a first chamber and a second chamber;wherein the proximal end portion of the inner tube is in fluidcommunication with the first chamber and the proximal end portion of theouter tube is in fluid communication with the second chamber.

The ablation electrode assembly includes an electrical conduitelectrically connected to the outer tube of the needle electrodeassembly; a first fluid conduit fluidly connected to the first chamber;and a second fluid conduit fluidly connected to the second chamber.

According to yet another aspect of the present disclosure, an ablationsystem for ablating tissue in a living subject is provided. The ablationsystem includes an ablation electrode system including a needleelectrode assembly. The needle electrode assembly includes an outer tubehaving at least a conductive distal tip and defining a cavity therein;and an inner tube disposed at least partially within the cavity of theouter tube and defining a lumen therein.

The ablation electrode system further includes a hub assembly fluidlyconnected to the needle electrode assembly. The hub assembly defines afirst chamber and a second chamber; wherein a proximal end portion ofthe inner tube is in fluid communication with the first chamber and aproximal end portion of the outer tube is in fluid communication withthe second chamber.

The ablation system includes a source of electrosurgical energy; asource of fluid; an electrical conduit electrically interconnecting theouter tube of the needle electrode assembly and the source ofelectrosurgical energy; a first fluid conduit fluidly interconnectingthe source of fluid and the first chamber; and a second fluid conduitfluidly connected to the second chamber.

For a better understanding of the present invention and to show how itmay be carried into effect, reference will be made by way of example tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which constitute a part of the specification, exemplaryembodiments exhibiting various objectives and features hereof are setforth, specifically:

FIG. 1 is a perspective view of an ablation electrode system inaccordance with an embodiment of the present disclosure;

FIG. 2 is an enlarged perspective view of the ablation electrode systemof FIG. 1, with a handle half-section removed therefrom and a hubassembly disposed therein shown partially broken away;

FIG. 3 is a longitudinal cross-sectional view of the ablation electrodesystem of FIGS. 1 and 2;

FIG. 4 is an enlarged longitudinal cross-sectional view of the hubassembly of FIGS. 2 and 3;

FIG. 5 is a longitudinal cross-sectional view of the outer shell of thehub assembly of FIGS. 2-4, including a needle electrode shown operativeconnected thereto;

FIG. 6 is a perspective view an inner manifold of the hub assembly ofFIGS. 2-4;

FIG. 7 is a longitudinal cross-sectional view of the inner manifold ofFIG. 6;

FIG. 8 is a perspective view of an ablation electrode system accordingto an alternate embodiment of the present disclosure;

FIG. 9 is a longitudinal cross-sectional view of the ablation electrodesystem of FIG. 8;

FIG. 10 is a longitudinal cross-sectional view of the outer shell of thehub assembly of FIG. 9, including needle electrodes shown operativeconnected thereto;

FIG. 10A is a distal end view of the outer shell of the hub assembly ofthe ablation electrode system of FIG. 8;

FIG. 11 is a perspective view an inner manifold of the hub assembly ofFIG. 9;

FIG. 12 is a longitudinal cross-sectional view of the inner manifold ofFIG. 11;

FIG. 13 is a perspective view of an ablation electrode systemillustrating a strain relief member operatively associated therewith forsupport of the cables and/or conduits entering the handle;

FIG. 14 is a schematic perspective view of a strain relief member foruse with ablation electrode system;

FIG. 15 is a schematic longitudinal cross-sectional view of anotherstrain relief member shown supported in the handle of the ablationelectrode system;

FIG. 16 is a schematic longitudinal cross-sectional view of yet anotherstrain relief member shown supported in the handle of the ablationelectrode system;

FIG. 17 is a schematic perspective view of another strain relief memberfor use with ablation electrode system; and

FIG. 18 is a cross-sectional view of the strain relief member of FIG.17, as taken through 18-18 of FIG. 17.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of ablation electrode systems, in accordance with thepresent disclosure, will now be described in detail with reference tothe drawings figures wherein like reference numerals identify similar oridentical structural elements. As shown in the drawings and describedthroughout the following description, as is traditional when referringto relative positioning on a surgical instrument, device or apparatus,the term “proximal” refers to the end of the instrument, apparatus ordevice that is closer to the user and the term “distal” refers to theend of the apparatus that is further away from the user.

Referring initially to FIGS. 1-7, an electrode ablation system,according to an embodiment of the present disclosure, is generallydesignated as ablation system 100. Ablation system 100 includes ahousing or handle assembly 110, and at least one needle electrodeassembly 150 supported within and extending from housing assembly 110.Housing assembly 110 and needle electrode assembly 150 define a centrallongitudinal axis “X”.

As seen in FIGS. 1-3, housing assembly 110 includes a housing or handle112 having first half-section 112 a and a second half-section 112 bselectively connectable to one another (e.g., in a snap-fit manner) viaconnecting structure 114 or the like. In one embodiment, housing 112 hasa substantially conical shape defining a flattened proximal surface 116a and a flattened distal surface 116 b (FIGS. 2 and 3). Housing 112further includes an annular ramp-like structure 116 c extending from thesurface thereof. Ramp-like structure 116 c acts as a surface againstwhich an operators fingers contact for distal advancement of needleelectrode 150 into the patient and/or proximal withdrawal of needleelectrode 150 from the patient.

As seen in FIGS. 2-8, electrode ablation system 100 further includes ahub assembly 120 supported in housing 112 of housing assembly 110. Hubassembly includes a hub assembly outer shell 130 and a hub assemblyinner manifold 140 disposed within outer shell 130. Outer shell 130 andinner manifold 140 of hub assembly are each fabricated from a suitableelectrically non-conductive material.

As seen in FIGS. 2-5, hub assembly outer shell 130 includes a bodyportion 132 defining a central lumen 134 extending therethrough. Outershell 130 defines a central longitudinal axis “X1” extending throughcentral lumen 134. In an embodiment, when outer shell 130 is positionedin housing 112, the central longitudinal “X1” axis thereof at leastsubstantially aligns with the central longitudinal “X” axis of housing112 and needle electrode assembly 150. Central lumen 134 of outer shell130 includes a tapered distal end 136 defining a constricted passage 134a therethrough. Passage 134 a is sized to support and receive needleelectrode assembly 150 therein.

Body portion 132 of outer shell 130 may include an annular flange 138formed therearound. As seen in FIGS. 2 and 3, annular flange 138 ofouter shell 130 is receiveable in a complementary annular channel orgroove 118 formed or provided in housing 112. Accordingly, annularflange 138 and annular groove 118 cooperate to fix the location of hubassembly 120 relative to housing 112.

As seen in FIGS. 2-4, 6 and 7, inner manifold 140 is configured anddimensioned for support within lumen 134 of outer shell 130. Innermanifold 140 includes a body portion 142 defining a first or inflowlumen 144 a formed at least partially in a proximal end portion 142 bthereof. Inner manifold 140 further includes a second or outflow lumen144 b extending entirely therethrough. Inner manifold 140 furtherincludes a third lumen 144 c formed at least partially in a distal endportion 142 a thereof.

As seen in FIGS. 3, 4, 6 and 7, inner manifold 140 defines a firstrecess 148 formed therein such that when inner manifold 140 is insertedinto lumen 134 of outer shell 130, first recess 148 defines a firstcavity or chamber 122 between outer shell 130 and inner manifold 140. Asseen in FIGS. 3 and 4, first lumen 144 a and third lumen 144 c are eachin fluid communication with first chamber 122.

With continued reference to FIGS. 3 and 4, when inner manifold 140 isinserted into lumen 134 of outer shell 130, a second chamber 124 isdefined in tapered distal end 136 of outer shell 130. When innermanifold 140 is so positioned, second lumen 144 b of manifold 140 is influid communication with the second chamber 124.

As seen in FIGS. 3, 4, 6 and 7, body portion 142 of inner manifold 140may include an annular groove 142 a formed therein. As seen in FIGS. 3and 4, annular groove 142 a of body portion 142 of inner manifold 140 isconfigured and dimensioned to receive a complementary annular flange orrib 128 formed in body portion 132 of outer shell 130. Accordingly,annular flange 128 and annular groove 142 c cooperate to fix thelocation of inner manifold 140 relative to outer shell 130.

In addition, as seen in FIG. 4, a glue “G”, including and not limitedto, adhesives, epoxies, bonding agents, cements, silicones and the like,is applied in a proximal or rear portion of lumen 134 of outer shell130, on a proximal or rear surface of inner manifold 140, and atlocations therebetween. Glue “G” functions to further secure innermanifold 140 within outer shell 130 and to create a seal between outershell 130 and inner manifold 140 to thereby inhibit and/or prevent theescape of fluid from therebetween.

In an embodiment, as seen in FIGS. 2-4, hub assembly 120 includes a sealelement 126 (e.g., an O-ring) disposed between body portion 132 of outershell 130 and body portion 142 of inner manifold 140. Seal element 126functions to reduce and/or prevent fluid from traveling between firstchamber 122 and second chamber 124.

As seen in FIGS. 1-4, a first or in-flow conduit 10 is fluidly connectedto first lumen 144 a of inner manifold 140. A distal end of firstconduit 10 extends through housing 112 of housing assembly 110 and isfrictionally inserted into first lumen 144 a of inner manifold 140 ofhub assembly 120.

With continued reference to FIGS. 1-4, a second or out-flow conduit 20is fluidly connected to second lumen 144 b of inner manifold 140.Desirably, a distal end of second conduit 20 extends through housing 112of housing assembly 110 and is frictionally inserted into second lumen144 b of inner manifold 140 of hub assembly 120.

Turning now to FIGS. 1-5, needle electrode assembly 150 is described ingreater detail. Needle electrode assembly 150 includes an outer tube 152a having an exposed distal end portion 154 a terminating in a sharpeneddistal tip 156 a which is constructed so as to penetrate tissue with aminimum risk of hemorrhage from the puncture tract. Outer tube 152 a isconstructed from a suitable electrically conductive material. Outer tube152 a includes a proximal end portion 158 a supported in housing 112,and in an embodiment, in a distal lumen 134 b formed in and extendingdistally from constricted passage 134 a of outer shell 130, as seen inFIGS. 4 and 5. Outer tube 152 a is hollow and defines a cavity 160 atherein.

In an embodiment, the non-exposed part of outer tube 152 a may besurrounded by a suitable insulating material. The insulating materialmay be any material which is biologically acceptable and suitable forinsertion into tissue. Since distal end portion 154 a is exposed ornon-insulated, distal end portion 154 a is capable of DC or AC delivery,preferably RF delivery.

Needle electrode assembly 150 further includes an inner tube 152 bdisposed substantially co-axially within cavity 160 a of outer tube 152a. Inner tube 152 b includes a distal end portion 156 b (see FIGS. 6 and7) located near distal end portion 154 a of outer tube 152 a and aproximal end portion 158 b extending from proximal end portion 158 a ofouter tube 152 a. Proximal end portion 158 b of inner tube 152 b extendsthrough constricted passage 134 a and into or through third lumen 144 cof inner manifold 140. It is envisioned that proximal end portion 158 bof inner tube 152 b is in fluid communication with first cavity orchamber 122 defined between inner manifold 140 and outer shell 130, seeFIGS. 2-4.

In use, cooling fluid “F” is delivered to distal tip 156 a of outer tube152 a from in-flow conduit 10. In particular, cooling fluid “F” travelsfrom in-flow conduit 10, into first chamber 122, into lumen 160 b (seeFIGS. 6 and 7) of inner tube 152 b of needle electrode assembly 150, todistal tip 156 a of outer tube 152 a. Cooling fluid “F” is led away fromdistal tip 156 a of outer tube 152 a through cavity 160 a, throughsecond chamber 124, through second lumen 144 b of inner manifold 140,and out through out-flow tube 20. Cooling fluid “F” may be communicatedto a collecting container (not shown) or back to a source of fluid “SF”(see FIG. 1) for re-circulation. Circulation of cooling fluid “F” may beestablished with the use of a suitable pump (not explicitly shown).

As seen in FIGS. 2, 3, 6 and 7, electrode ablation system 100 furtherincludes a first electrical conduit 170 extending through housing 112and electrically connected to outer tube 152 a of needle electrodeassembly 150. In particular, first electrical conduit 170 includes adistal end 170 a electrically connected to outer tube 152 a at alocation distal of hub assembly 120 and within housing 112. Firstelectrical conduit 170 is also electrically connected to a source ofelectrosurgical energy “E”. Accordingly, electrosurgical energy may bedelivered from the source of electrosurgical energy, through firstelectrical conduit 170, to outer tube 152 a.

As seen in FIGS. 2, 4, 6 and 7, electrode ablation system 100 furtherincludes a thermocouple assembly 172 operatively associated with innertube 152 b. Thermocouple assembly 172 includes a first wire orthermocouple 174 extending through lumen 160 b of inner tube 152 b. Adistal end 174 a of first wire 174 is desirably electrically secured todistal end portion 156 b of inner tube 152 b, as by, for example,soldering and the like. First wire 174 may be fabricated from constantan(i.e., a high-resistance alloy of approximately 40% nickel and 60%copper). However, other suitable materials may be used for first wire174, such as, for example, any suitable conductor that is dissimilarfrom inner tube 152 b (e.g., stainless steel) such that a thermocoupleis created between the two materials.

Thermocouple assembly 172 further includes a second wire 176 having adistal end 176 a electrically connected to inner tube 152 b. In anembodiment, distal end 176 a of second wire 176 is connected to aproximal end portion 158 b of inner tube 152 b. Second wire 176functions to electrically interconnect first wire 174 and a thermocouplemeasuring circuit. Accordingly, a temperature measurement signal fromthe thermocouple measuring circuit may then be sent to anelectrosurgical energy source “E” and/or a central processing unit formonitoring.

As seen in FIGS. 1, 2 and 7, each of electrical conduit 170, first wire174 and second wire 176 may be contained in a single cable 180.

Turning now to FIGS. 8-12, an electrode ablation system, in accordancewith another embodiment of the present disclosure, is generallydesignated as 200. Electrode ablation system 200 is substantiallysimilar to ablation system 100 and will be discussed in detail to theextent necessary to identify differences in construction and operation.Unlike electrode ablation system 100, which includes a single needleelectrode assembly 150, electrode ablation system 200 includes threeneedle electrode assemblies 250 a-250 c extending distally from housing112 of housing assembly 110. While a single and three needle electrodeassemblies have been shown and described herein, any suitable number ofneedle electrode assemblies may be provided.

As seen in FIGS. 9-12, hub assembly 220 of electrode ablation system 200includes a hub assembly outer shell 130 and a hub assembly innermanifold 240 operatively disposed within outer shell 230.

As seen in FIGS. 9, 10 and 10A, hub assembly outer shell 230 includes abody portion 232 defining a central lumen 234 extending therethrough.Desirably, outer shell 230 includes three constricted passages 236 a-236c extending through a distal end portion 230 a of outer shell 230 and influid communication with central lumen 234. Desirably, each passage 236a-236 c is sized to support and receive a proximal end of outer tube 252a of a respective needle electrode assembly 250 a-250 c.

As seen in FIGS. 9, 11 and 12, inner manifold 240 is configured anddimensioned for support within lumen 234 of outer shell 230. Innermanifold 240 includes a body portion 242 defining a first or inflowlumen 244 a formed at least partially in a proximal end portion 242 bthereof. Inner manifold 240 further includes a second or outflow lumen244 b extending entirely therethrough. Inner manifold 240 furtherincludes a plurality of third lumens 244 c formed at least partially ina distal end portion thereof 242 a. Each third lumen 244 c of innermanifold 240 is configured and dimensioned to receive and support aproximal end of a respective inner tube 252 b of needle electrodeassemblies 250 a-250 c therein.

As seen in FIGS. 9, 11 and 12, inner manifold 240 defines a first recess248 formed therein such that when inner manifold 240 is inserted intolumen 234 of outer shell 230, first recess 248 defines a first cavity orchamber 222 between outer shell 230 and inner manifold 240. As can beappreciated and similar to hub assembly 120 of electrode ablation system100, first lumen 244 a and each third lumen 244 c are in fluidcommunication with first chamber 222.

With continued reference to FIGS. 9, 11 and 12, when inner manifold 240is inserted into lumen 234 of outer shell 230, a second chamber 224 isdefined in distal end portion 236 of lumen 234 of outer shell 230. Wheninner manifold 240 is so positioned, second lumen 244 b of manifold 240is in fluid communication with the second chamber 224.

As seen in FIGS. 9-12, each needle electrode assembly 250 a-250 c ofelectrode ablation system 200 is substantially similar to needleelectrode assembly 150 of electrode ablation system 100, and thereforereference may be made to the detailed discussion of needle electrodeassembly 150 for an understanding and description of needle electrodeassemblies 250 a-250 c.

Use of electrode ablation system 200 will now be described in detail. Inuse, cooling fluid “F” is delivered to a distal tip 256 of each outertube 252 a. In particular, cooling fluid travels from in-flow conduit10, into first chamber 222, into a lumen of an inner tube (see FIGS. 6and 7) of each needle electrode assembly 250 a-250 c, to a distal tip256 of the outer tube of each needle electrode assembly 250 a-250 c. Thecooling fluid is led away from distal tip 256 of the outer tube of eachneedle electrode assembly 250 a-250 c, through second chamber 224,through second lumen 244 b of inner manifold 240, and out throughout-flow tube 20.

As seen in FIGS. 11 and 12, a first wire 174 of thermocouple assembly172 extends through lumen 160 b (see FIG. 6) of at least one inner tube252 b of needle electrode assemblies 250 a-250 c. As mentioned above, adistal end 174 a of first wire 174 is desirably electrically secured toa distal end portion of inner tube 252 b, as by, for example, solderingand the like. Desirably, first wire 174 is fabricated from constantan orthe like (i.e., a high-resistance alloy of approximately 40% nickel and60% copper). A second wire 176 of thermocouple assembly 172 has a distalend electrically connected to inner tube 252 b.

The handle of needle electrode system 200 is configured and adapted soas to maintain needle electrode assemblies 250 a-250 c substantiallyparallel to one another during insertion and/or placement of needleelectrode assemblies 250 a-250 c into a target surgical site.

Turning now to FIGS. 13-18, electrode ablation systems 100, 200 may eachinclude an adjustable cord strain relief member 50 operatively disposedon cable 180, in-flow conduit 10, and/or out-flow conduit 20. Strainrelief member 50 is configured and dimensioned for operative engagementin an aperture 114 (see FIGS. 1 and 2) of housing 112 of handle assembly110. In an embodiment, aperture 114 is formed in a side of housing 112of handle assembly 110 such that cable 180, in-flow conduit 10 and/orout-flow conduit 20 may extend out of the side thereof. By having cable180, in-flow conduit 10 and/or out-flow conduit 20 exit from a side ofhousing 112 of handle assembly 110 a strain relief for cable 180,in-flow conduit 10 and/or out-flow conduit 20 is established.

Strain relief member 50 includes a body portion 52 having asubstantially hour-glass configuration. Body portion 52 may include afirst substantially spherical portion 52 a and a second substantiallyspherical portion 52 b. Desirably, second portion 52 b of body portion52 is poly-axially supported (e.g., in the manner of a ball and socketjoint) within a complementarily sized and shaped aperture 114.

As seen in FIGS. 14-16, an annular rib 54 a may be provided on thesurface of second body portion 52 a for engaging the inner surface ofshaped aperture 114. Strain relief member 50 may also be provided with ashield or apron 56 extending radially therefrom. Shield 56 may bedisposed within an appropriately sized recess 116 formed in handle 112,as seen in FIG. 15, or may be disposed externally of handle 112, as seenin FIG. 16.

As seen in FIGS. 17 and 18, strain relief member 50 may include meansfor locking including a tapered portion 52 c disposed between first bodyportion 52 a and second body portion 52 b, and at least onelongitudinally oriented locking rib 54 b projecting from tapered portion52 c. Locking rib 54 b is configured and dimensioned to selectivelyengage complementary channels 118 formed in handle 112. In use, asstrain relief member 50 is moved in a first direction (as indicated byarrow “A”), locking rib 54 b disengages channels 118 to unlock strainrelief member 50, and as strain relief member 50 is moved in a seconddirection (opposite to direction “A”), locking rib 54 b engages channels118 to lock strain relief member 50.

The foregoing description is merely a disclosure of particularembodiments and is no way intended to limit the scope of the invention.Other possible modifications are apparent to those skilled in the artand all modifications are to be defined by the following claims.

1. An ablation electrode system for use with a source of electrosurgicalenergy to ablate tissue in a living subject, the ablation electrodesystem comprising: a handle assembly; a needle electrode assemblysupported in and extending from the handle assembly, the needleelectrode assembly including: an outer tube having at least a conductivedistal tip, a proximal end portion supported in the handle assembly, anddefining a cavity therein; and an inner tube disposed at least partiallywithin the cavity of the outer tube and having a proximal end portionsupported within the handle assembly, the inner tube defining a lumentherein; a hub assembly supported within the handle assembly and fluidlyconnected to the needle electrode assembly, the hub assembly including:an outer shell defining a lumen therein; and an inner manifoldoperatively supported in the lumen of the outer shell, the innermanifold and the outer shell being configured and dimensioned so as todefine a first chamber and a second chamber therebetween; wherein theproximal end portion of the inner tube is in fluid communication withthe first chamber and the proximal end portion of the outer tube is influid communication with the second chamber; an electrical conduitelectrically connected to the outer tube of the needle electrodeassembly; a first fluid conduit fluidly connected to the first chamber;and a second fluid conduit fluidly connected to the second chamber. 2.The ablation electrode assembly according to claim 1, wherein the outertube of the needle electrode assembly is fabricated from an electricallyconductive material.
 3. The ablation electrode assembly according toclaim 2, wherein a layer of insulative material is disposed on an outersurface of the outer tube and wherein the distal tip of the outer tip isexposed.
 4. The ablation electrode assembly according to claim 3,wherein the inner tube delivers fluid to the distal tip of the outertube.
 5. The ablation electrode assembly according to claim 4, furthercomprising a thermocouple assembly electrically connected to the innertube.
 6. The ablation electrode assembly according to claim 5, whereinthe thermocouple assembly includes a constantan wire extending throughthe lumen of the inner tube and electrically connected to a distal endof the inner tube.
 7. The ablation electrode assembly according to claim6, wherein the inner manifold defines a lumen therein interconnectingthe second chamber of the hub assembly to the second fluid conduit. 8.The ablation electrode assembly according to claim 7, wherein anadhesive is applied to at least one of a proximal end of the innermanifold and the outer shell to secure the inner manifold within theouter shell and to seal the hub assembly from fluid leaks from betweenthe outer shell and the inner manifold.
 9. The ablation electrodeassembly according to claim 7, wherein a seal element is providedbetween the outer shell and the inner manifold of the hub assembly toprevent transmission of fluid between the first chamber and the secondchamber.
 10. The ablation electrode assembly according to claim 7,further comprising a plurality of needle electrode assemblies aresupported in and extend from the handle assembly, wherein a proximal endportion of each inner tube is in fluid communication with the firstchamber and a proximal end portion of each outer tube is in fluidcommunication with the second chamber.
 11. The ablation electrodeassembly according to claim 10, wherein the thermocouple assemblyincludes a constantan wire extending through the lumen of at least oneinner tube and electrically connected to a distal end of said at leastone inner tube.
 12. The ablation electrode assembly according to claim1, wherein at least one of the electrical conduit, the first fluidconduit, and the second fluid conduit exit from a side of the handleassembly.
 13. An ablation electrode system for use with a source ofelectrosurgical energy to ablate tissue in a living subject, theablation electrode system comprising: a handle assembly; a needleelectrode assembly supported in and extending from the handle assembly,the needle electrode assembly including: an outer tube having at least aconductive distal tip, a proximal end portion supported in the handleassembly, and defining a cavity therein; and an inner tube disposed atleast partially within the cavity of the outer tube and having aproximal end portion supported within the handle assembly, the innertube defining a lumen therein; a hub assembly supported within thehandle assembly and fluidly connected to the needle electrode assembly,the hub assembly defining a first chamber and a second chamber; whereinthe proximal end portion of the inner tube is in fluid communicationwith the first chamber and the proximal end portion of the outer tube isin fluid communication with the second chamber; an electrical conduitelectrically connected to the outer tube of the needle electrodeassembly; a first fluid conduit fluidly connected to the first chamber;and a second fluid conduit fluidly connected to the second chamber. 14.The ablation electrode assembly according to claim 13, wherein the outertube of the needle electrode assembly is fabricated from an electricallyconductive material.
 15. The ablation electrode assembly according toclaim 14, wherein a layer of insulative material is disposed on an outersurface of the outer tube and wherein the distal tip of the outer tip isexposed.
 16. The ablation electrode assembly according to claim 15,wherein the inner tube delivers fluid to the distal tip of the outertube.
 17. The ablation electrode assembly according to claim 16, furthercomprising a thermocouple assembly electrically connected to the innertube.
 18. The ablation electrode assembly according to claim 17, whereinthe thermocouple assembly includes a constantan wire extending throughthe lumen of the inner tube and electrically connected to a distal endof the inner tube.
 19. The ablation electrode assembly according toclaim 18, wherein an inner manifold defines a lumen thereininterconnecting the second chamber of the hub assembly to the secondfluid conduit.
 20. The ablation electrode assembly according to claim19, wherein the hub assembly includes an outer shell defining a lumentherein and an inner manifold operatively supported in the lumen of theouter shell.
 21. The ablation electrode assembly according to claim 20,wherein an adhesive is applied to at least one of a proximal end of theinner manifold and the outer shell of secure the inner manifold withinthe outer shell and seal the hub assembly from fluid leaks from betweenthe outer shell and the inner manifold.
 22. The ablation electrodeassembly according to claim 20, wherein a seal element is providedbetween the outer shell and the inner manifold of the hub assembly toprevent transmission of fluid between the first chamber and the secondchamber.
 23. The ablation electrode assembly according to claim 20,further comprising a plurality of needle electrode assemblies aresupported in and extend from the handle assembly, wherein a proximal endportion of each inner tube is in fluid communication with the firstchamber and a proximal end portion of each outer tube is in fluidcommunication with the second chamber.
 24. The ablation electrodeassembly according to claim 23, wherein the thermocouple assemblyincludes a constantan wire extending through the lumen of at least oneinner tube and electrically connected to a distal end of said at leastone inner tube.
 25. The ablation electrode assembly according to claim13, wherein at least one of the electrical conduit, the first fluidconduit, and the second fluid conduit exit from a side of the handleassembly.
 26. An ablation system for ablating tissue in a livingsubject, the ablation system comprising: an ablation electrode systemcomprising: a needle electrode assembly including: an outer tube havingat least a conductive distal tip and defining a cavity therein; and aninner tube disposed at least partially within the cavity of the outertube and defining a lumen therein a hub assembly fluidly connected tothe needle electrode assembly, the hub assembly defining an enlargedfirst chamber and an enlarged second chamber; wherein a proximal endportion of the inner tube is in fluid communication with the firstchamber and a proximal end portion of the outer tube is in fluidcommunication with the second chamber; a source of electrosurgicalenergy; a source of fluid; an electrical conduit electricallyinterconnecting the outer tube of the needle electrode assembly and thesource of electrosurgical energy; a first fluid conduit fluidlyinterconnecting the source of fluid and the first chamber; and a secondfluid conduit fluidly connected to the second chamber, wherein the hubassembly includes a shell and a manifold disposed within the shell,wherein the first chamber and the second chamber are defined by spacesbetween the shell and the manifold.